I'm going to throw this out there, so just consider that when reading...
I was down by LA, in CA, and went a visited a campfire friend at a local range. He had a friend who was firing some Swiss rifle IIRC, that he had necked up 6.5 x 55 brass, to 30 caliber. When he was done, he gave me the brass, and said he only loads new brass and then toss it.
I brought it home and my 6.5 x 55 dies, wouldn't even neck it down, and wouldn't get pass the shoulder much, no matter how much I had lubed it.
So I just threw the brass in an empty butter container ( Shed's Spread) and let it sit for a month or two just ignoring it. I had never wiped the oil on the case off. It was Amzoil version of WD 40.
Couple months later, I was just going to throw it out, but I thought I'd try to run a couple cases thru the 6.5 x 55 Die one last time before getting rid of it.
After the oil sitting on it for a while, it all went thru the die like butter. Guess the oil on it and sitting ( probably didn't need the entire 60 days or so) softened the brass up enough, it worked just fine.
Did the same thing on 243 brass that wouldn't chamber in my rifle....used range pick up.. evidently once fired...think it was ran thru a pump Remington...
Lubed it, let it sit for two days in a disposable plastic container, and resized it just fine....
So just passing that on about brass that was hard to resize, to fit a different rifles chamber. No guarantees implied... both that worked for me several times.
Sacrificing a chicken over it and do a Louisiana Cajun Voodoo chant didn't work so well...
